The present invention relates to an apparatus for heating and conveying a granular material, such as aggregate to be used in the manufacture of asphalt pavement, or recycled asphalt pavement, or oil contaminated soil.
In the production of asphalt pavement, it is known to heat granular materials, such as stone aggregate, in a rotary drum where the material to be heated is in direct contact with the hot gases coming from a burner. It is also known to heat granular materials in a screw conveyor which has hollow flights through which a heating fluid is circulated.
The above and other known processes for heating granular materials have disadvantages in the case of some materials, such as heat sensitive materials. For example, in the case of a screw conveyor, it is possible for a portion of the granular material to remain in contact with the heated flights throughout its passage through the conveyor, and so as to be overheated, while other portions are inadequately heated.
It is accordingly an object of the present invention to provide a heating and conveying apparatus for granular materials, and which overcomes the disadvantages and limitations of the prior systems.
It is also an object of the present invention to provide a heating and conveying apparatus which provides efficient transfer of heat to a granular material without exposing the material to excessively high temperatures, and which achieves substantially uniform heating of all portions of the material.
It is a further object of the present invention to provide a heating and conveying apparatus of the described type which has the ability to conveniently enclose the process so as to permit any released gases to be captured.